Valve cover breather?

[KCz Eclipse]

Okay, so I've been looking at some pictures of 4g63 engines. While looking at the pictures I noticed many of the people had removed the tube on the left side of the valve cover and replaced it with a thing that looked like a mini filter. So with a little research found out it is called a valve cover breather. However, I wasn't able to find the purpose of the breather. So for my question; what is the real purpose of the breather? Could oil leak out of the breather at all? Is there a plus to using a breather versus the normal tube? I just think they look cool, and if they don't have any real cons, would like to get one. Any info on these things would be helpful.


Thanks

 

[mikesx4911]

That was one of my first mods that I did .

 

[Calan]

Some good pics/ideas here:

Vented Valve Cover Post up some pics! - Honda-Tech

Even better ones on this site if you search... DSMs even!